In recent years, many digital home-electric appliances, such as content playback devices for playing back music contents, movie contents or the like, are implemented with functions to encrypt and decrypt data for copyright protection (see Patent Documents 1-2) or are implemented with program update functions to, after sales, add new functions or correct bugs.
Patent Document 1: Japanese Patent Application Publication No. 2-155034
Patent Document 2: Japanese Patent Application Publication No. 4-102920
Patent Document 3: Japanese Patent Application Publication No. 2001-318787
Non-Patent Document 1: Lei, D., Thekkath, C. A., Mitchell, M., Lincoln, P., Boneh, D., Mitchell, J. C. and Horowitz, M.: Architechtural Support for Copy and Tamper Resistant Software, In Proceedings of the 9th Inte'l Conference on Architectural Support for Programming Languages and Operating Systems (ASPLOS-IX), pages 169-177, November 2000.Non-Patent Document 2: E. Suh, D. Clarke, B. Gassend, M. van Dijk, and S. Devadas. The AEGIS processor architecture for tamper evident and tamper resistant processing. Technical Report LCS-TM461, Massachusetts Institute of Technology, February 2003.